The present invention relates to a unique method for preparing p-aminodiphenylamine from N-phenylquinoneimine. P-aminodiphenylamine is useful in the production of numerous rubber chemicals such as antidegradants, gel inhibitors and polymerization inhibitors.
P-aminodiphenylamine (also known as N-phenyl-p-phenylenediamine) has been made by a variety of methods known to those skilled in the art. For example, Japanese Application 125343-1981 discloses a process for the preparation of N-phenyl-p-phenylenediamine by reacting N-arylaminophenol with ammonia in the presence of an acidic catalyst and polycyclic aromatic compound. The process disclosed in Japanese Application No. 125343-1981 is characterized by a one step, one pot procedure. However, preparation of the products by this procedure would necessitate the use of elaborate distillation equipment to remove the polycyclic aromatic compounds that are employed. The removal of the polycyclic aromatic compounds further contributes to the expense of manufacturing the p-aminodiphenylamine. Since demand for p-aminodiphenyamine is on the increase, there is a need for a new and more efficient process for its production.